Objectives:Staphylococcus aureus and Staphylococcus epidermidis are the major cause of infections associated with implanted medical devices, such as intravascular catheters, prosthetic heart valves and orthopaedic devices. Colonisation on abiotic and biotic surfaces is often sustained by biofilm forming strains. Human natural defences can interfere with this virulence factor. In these experiments we investigated the effect of human apo-transferrin (apo-TF, the iron-free form of an iron-binding serum glycoprotein) and holo-transferrin (holo-TF, the iron-saturated form) on biofilm formation by S. aureus and S. epidermidis. For S. aureus the effect of apo-TF and holo-TF on the adhesion/invasion ability on human cell lines was also studied.

Methods: We used two S. epidermidis strains (1 clinical isolate and ATCC35984 strain) and two S. aureus strains (1 clinical isolate and ATCC6538P strain). Apo-TF and holo-TF were used at concentrations starting from physiological (34 mg/ml) up to non-bacteriostatic and non-bactericidal. Bacterial biofilm formation was assessed by Christensen assay. S. aureus adhesion and invasion assays were performed in HeLa cell lines. Bacterial invasion was determined by numbering viable bacteria resistant to gentamicin treatment 1 h after infection. Bacterial adhesion was calculated as difference between total bacterial count and bacterial invasion count, 1 h after infection.

Results: Both transferrins (TFs) do not possess bacteriostatic and bactericidal effects. A strong reduction in biofilm formation with both TFs was obtained. In particular, the reduction in biofilm formation was higher with holo-TF rather than obtained with apo-TF. Both TFs exerted a significant reduction of S. aureus adhesion to and invasion of HeLa cells. SDS-PAGE and zymogram analyses are ongoing in order to compare surface protein profiles of treated and non treated samples.

Conclusion: Our results suggest that both forms of TF could be used for antibacterial adjuvant therapy in infection sustained by staphylococci to strongly reduce their virulence related to adhesion and invasion.

Session Details

Date:

16/05/2009

Time:

00:00-00:00

Session name:

19th European Congress of Clinical Microbiology and Infectious Diseases